Polarized self-neutralizing servomotor



Nov. 20, 1956 F. R. ADAMS POLARIZED SELF-NEUTRALIZING SERVOMOTOR Filed Nov. 16, 1953 I IN V EN TOR. @fiA/K 18/4 04) 5 BY 44% m A 7" TOEA/E'Yj United States Patent POLARIZED SELF-NEUTRALIZING SERVOMOTOR Frank R. Adams, Janesville, Wis.

Application November 16, 1953, SerialNo. 392,168

4 Claims. (Cl. 317-172) This invention relates to a polarized self-neutralizing servo-motor.

An electromagnet having a centrally tapped coil, or otherwise provided with separately energized coils to effect opposite movements of its armature, hasarms leading from its core to arcuate'pole pieces closely spaced at opposite sides of an armature shaft which is substantially normal to the plane of the pole pieces. Between the pole pieces and the coil the shaft carries a horseshoe magnet in the form of a channel, the flanges of which constitute its north and south poles. From an intermediate position the armature and the shaft upon which it is mounted will oscillate clockwise or counterclockwise according to which coil is energized, and which pole piece becomes magnetized north and which becomes magnetized south.

A feature of the device is its ability to assume automatically, as soon as the windings are deenergized, an intermediate position from which the polarized armature can be caused to move in either direction as above described.

The device is useful, for example, in operating the rudder of a model airplane or a boat to the right or the left as determined by remote radio control. An entirely different field of use involves the operation of a double throw switch by means of the armature shaft.

In the drawings:

Fig. 1 is a view showing my servo-motor in perspective.

Fig. 2 shows the motor in side elevation with portions broken away to an axial section.

Fig. 3 is a view taken in section on line 33 of Fig. 1, the intermediate or neutral position of the polarized armature being shown in dotted line.

On the core 5 of the electromagnet is a winding 6 which may either comprise separate coils with a common central tap 7 or, as an electrical equivalent, a single coil with a central tap 7 and terminal leads 8 and 9. Extending in parallelism with each other from the ends of the core 5 are polar arms 10 and 11 respectively provided integrally with segmental pole pieces 12 and 13 which are substantially semi-circular in outline spaced only by a narrow transverse gap 14 best shown in Fig. 3. Connected with pole pieces 12 and 13 by nuts on the mounting screws 15, 16 is a non-magnetic disk 17 which may be made of brass or the like and which supports a tubular bearing 18 for the armature shaft 19. This shaft is connected centrally with a channel shaped magnet 20, desirably made of one of the currently available alloys to have high magnetic strength. The flanges 21, 22 of the channel shaped magnet 20 comprise poles. For convenience, the polarity is indicated in Fig. 1, the pole 22 being marked N and the pole 21 being marked 8. These poles rotate in a plane which is parallel to the plane of the electromagnetically energized pole pieces 12 and 13 as clearly appears in Fig. 1 and Fig. 2. A non-magnetic spacer at 24 may be used to limit the approach of thepermanent-magnet poles 21, 22 to the electromagnetically,energizable poles 12, 13.

By, reason of the permanent magnetism of armature 20, the armature is polarized, whereas the electromagnetically energized poles 12 and 13 may be reversed in polarity at will,. according to which section of the coil is energized. Pole 12 may be a north pole or a south pole according .to whether currentflows from tap 7 to lead 8 or to lead 9. Fig. 1 shows the parts in the position-assumedbythe armature 20 and the armatureshaft 19 when pole 12 is a north pole and pole'13 is a south pole. If the other section of the coil 6 were tobe energized, the polarity of poles 12 and13 would be reversed. Pole 12 would become a south pole.. .Thereupon the polarized armature 20 would move from the position shown in Fig. 1 to a-position in which its pole 22 would be proximate pole 12.

With the coil 6 wholly de-energized, the poles 12 and 13 will likewise be de-energized and will thereupon become merely an armature means for completing a magnetic flux circuit between the poles 21 and 22 of the permanent magnet 20. This magnet will thereupon adjust itself .to a position in which a maximum amount of flux can pass through the poles 12 and 13. This position is not necessarily one in which the permanent magnet 29 is at right angles to the gap 14. The armature 20 is self-neutralizing merely to some position intermediate the two extreme positions which it is capable of taking when one or the other section of coil 6 is energized.

It may be explained also, that in practice I do not ordinarily permit the armature shaft to swing through a full 180 of movement since, in the position shown in Figs. 1 and 2, it tends to get on dead center and does not easily neutralize itself to the aforesaid intermediate position. Therefore, in order to take full and prompt advantage of the capacity of the armature to return to some intermediate position when coil 6 is de-energized, I desirably connect the shaft 19 to whatever mechanism is to be operated thereby in such a manner as to limit the oscillation of the shaft to preclude it from moving to the extreme positions shown in Figs. 1 and 2. Since this is readily accomplished in the connection to the operated mechanism, no limiting means is illustrated.

As above indicated, it is immaterial to the present invention what apparatus is actuated by shaft 19 of the servo-motor as above described. Both in the case of the model airplane and in the case of a double throw switch there are advantages in a servo-motor which is automatically and inherently self-neutralizing to an intermediate position when tie-energized and will oscillate instantly clockwise or counterclockwise from such position according to its energization.

As above indicated, it is immaterial to the present invention what apparatus is actuated by shaft 19 of the servo-motor as above described. Both in the case of the model airplane and in the case of a double throw switch there are advantages in a servo-motor which is automatically and inherently self-neutralizing to an intermediate position when de-energized and will oscillate instantly clockwise or counterclockwise from such position according to its energization.

I claim:

1. A light weight and compact servo-motor comprising an electromagnet having a core, a winding on the core, substantially parallel polar arms connected to the ends of the core, said arms extending laterally from the core and having inturned ends with spaced apart margins comprising pole pieces for said electromagnet, a nonmagnetic plate mounted on said pole pieces and spanning the space therebetween, said plate constituting a connector for tying together the ends of said arms, said plate being provided with a bearing between said pole pieces, a rock shaft rotatable in said bearing on an axis transverse to said core, and a polarized armature'mounted on the rock shaft and having the form of a channel with elongated polar flanges rotatable in a plane substantially parallel to that of the pole pieces and adapted inherently to span the gap between the pole pieces when the coil is de-energized, the flanges of the polarized armature being adapted to align themselves at opposite sides of the gap with particular pole pieces when the coil is energized.

2. The device of claim 1 in which the coil comprises two sections of opposite polarity whereby the energization is reversable according to which coil is energized, the armature and its shaft being oscillatable clockwise and counterclockwise from its first mentioned position according to the coil section Which is energized.

3. The device of claim 1 in which the non-magnetic plate laps said pole pieces and is provided with shouldered recesses to receive said pole pieces, the lapping portions of said plate and said pole pieces being provided with aligned apertures, and bolts in said apertures for connecting said plateand pole pieces, said bolts having threaded extensions by which the entire servo-motor may be mounted.

4. A servo-motor of the character described comprising the combination with a core, of a coil on the core having a central tap and end leads whereby said coil comprises separate sections energizable for reversing the polarity of the core, parallel arms projecting substantially at right angles from the core, segmental and substantially semi-circular pole pieces carried by the arms and projecting toward each other from the arms in a plane substantially parallel to the core, said pole pieces having margins spaced to provide a transversely extending gap, a non-magnetic mounting plate connected with the respective pole pieces and provided with a bearing at said gap, an armature shaft oscillatable in the bearing and extending through said gap between the pole pieces, a polarized armature comprising a channel shaped magnet centrally mounted on the armature shaft between the pole pieces and the coil and having polar flanges projecting toward the pole pieces and rotatable in a plane parallel thereto, said flanges inherently assuming intermediate position in which they extend across the gap when the coil sections are de-energized, the armature and its shaft being oscillatable clockwise and counterclockwise from said intermediate position in a direction determined by the polarity of the pole pieces according to the coil section which is energized.

References Cited in the file of this patent UNITED STATES PATENTS 

